Scavenger receptor class B type I (SR-BI) is involved in vitamin E transport across the enterocyte

J Biol Chem. 2006 Feb 24;281(8):4739-45. doi: 10.1074/jbc.M509042200. Epub 2005 Dec 27.


Although cellular uptake of vitamin E was initially described as a passive process, recent studies in the liver and brain have shown that SR-BI (scavenger receptor class B type I) is involved in this phenomenon. As SR-BI is expressed at high levels in the intestine, the present study addressed the involvement of SR-BI in vitamin E trafficking across enterocytes. Apical uptake and efflux of the main dietary forms of vitamin E were examined using Caco-2 TC-7 cell monolayers as a model of human intestinal epithelium. (R,R,R)-gamma-tocopherol bioavailability was compared between wild-type mice and mice overexpressing SR-BI in the intestine. The effect of vitamin E on enterocyte SR-BI mRNA levels was measured by real-time quantitative reverse transcription-PCR. Concentration-dependent curves for vitamin E uptake were similar for (R,R,R)-alpha-, (R,R,R)-gamma-, and dl-alpha-tocopherol. (R,R,R)-alpha-tocopherol transport was dependent on incubation temperature, with a 60% reduction in absorption at 4 degrees C compared with 37 degrees C (p < 0.05). Vitamin E flux in enterocytes was directed from the apical to the basal side, with a relative 10-fold reduction in the transfer process when measured in the opposite direction (p < 0.05). Co-incubation with cholesterol, gamma-tocopherol, or lutein significantly impaired alpha-tocopherol absorption. Anti-human SR-BI antibodies and BLT1 (a chemical inhibitor of lipid transport via SR-BI) blocked up to 80% of vitamin E uptake and up to 30% of apical vitamin E efflux (p < 0.05), and similar results were obtained for (R,R,R)-gamma-tocopherol. SR-BI mRNA levels were not significantly modified after a 24-h incubation of Caco-2 cells with vitamin E. Finally, (R,R,R)-gamma-tocopherol bioavailability was 2.7-fold higher in mice overexpressing SR-BI than in wild-type mice (p < 0.05). The present data show for the first time that vitamin E intestinal absorption is, at least in part, mediated by SR-BI.

MeSH terms

  • Absorption
  • Animals
  • Binding, Competitive
  • Biological Transport
  • CD36 Antigens / metabolism
  • CD36 Antigens / physiology*
  • Caco-2 Cells
  • Cell Differentiation
  • Cholesterol / metabolism
  • Dose-Response Relationship, Drug
  • Enterocytes / metabolism*
  • Epithelial Cells / metabolism
  • Humans
  • Intestinal Mucosa / metabolism
  • Lipids / chemistry
  • Mice
  • Mice, Transgenic
  • Micelles
  • RNA, Messenger / metabolism
  • Temperature
  • Time Factors
  • Tocopherols / metabolism
  • Vitamin E / metabolism*
  • alpha-Tocopherol / metabolism
  • gamma-Tocopherol / metabolism


  • CD36 Antigens
  • Lipids
  • Micelles
  • RNA, Messenger
  • Vitamin E
  • gamma-Tocopherol
  • Cholesterol
  • alpha-Tocopherol
  • Tocopherols